The incidence has been widely reported of post procedural infections associated with surgery or diagnostic studies. It is believed that a significant number of these infections are due to inadequate reusable instrument reprocessing.
Cleaning of instruments on an industrial scale involves two steps. In the first step the instrument is cleaned and in the second step it is disinfected normally to “high level disinfection” or “sterilization” standards. It is generally accepted that failure to adequately clean items after use in the first step may compromise the efficacy of the second. The elimination of human proteins from the instruments represents a significant challenge. The challenge has been made more difficult as medical instruments have been developed, for example endoscopes, which utilize materials that are neither temperature resistant nor chemically inert.
For effective cleaning of medical instruments a preparation should be effective for soil removal, effective for protein digestion and resist foaming. In addition, the products are required to have stability and a long shelf life.
These desiderata tend to be mutually inconsistent objectives. In order to avoid foaming, soil removal preparations used in hospital cleaning/sterilizing “reprocessing” systems have mainly utilized highly alkaline non-foaming detergents, but their use is incompatible with both enzymes, and with materials of construction of flexible endoscopes. The use of close to neutral “enzymatic detergents” (preparations including both enzymes and detergents) has been found to be relatively effective for removal of proteins and safe with endoscopes, and enables acceptable levels of soil removal to be achieved. However, while enzymes in “enzymatic detergents” help to remove proteins, surfactants have been needed to remove the fats and carbohydrates. Due to the incorporation of surfactants, “enzymatic detergents” tend to produce foam to an unacceptable extent.
Foaming is undesirable because it blocks the visualization of instruments in manual cleaning baths, impedes access of washing liquor to soils during manual cleaning and blocks water jets and washing liquor circulation in automated washers (e.g., tunnel washers). The foams tend to block the lumens of instruments preventing effective cleaning of the lumen interior. When enzyme based cleaners have been used in reprocessing machinery the foam tends to fill the volume thus impeding the cleaning cycle by disrupting jets and agitation. Furthermore it makes the machine difficult to unload, interfering with proper draining, and leaving foam residues containing pathogens which can contaminate following cleaning cycles giving rise to significant risk of cross infection since the cleaners do not kill the microorganisms which they dislodge from surfaces. Instruments covered with foam require additional handling and washing before they can be sterilized. Increasingly the additional labour cost, time, and water consumption costs are regarded as unacceptable. Multiple guidelines and standards recognise the problem and warn against using foaming detergents for cleaning medical instruments (e.g., AS 4187:2003 or AS 4815:2006).
Although this problem has been recognized, it has not to date been satisfactorily overcome. Two solutions to the foaming problem have been utilized, however to date neither approach has succeeded in satisfying the market need.
In the first approach antifoams have been added to the cleaning composition or washer, but that has been unsatisfactory because antifoams leave unacceptable residues on the medical instruments. In the second approach attempts have been made to use so called “low foaming” non-ionic detergents such as alkylene oxide adducts. These tend to leave an undesirable film of oily residue on treated surfaces similar to that from antifoams and also produce hazy solutions which reduce visibility during washing cycles.
As a consequence commercially available formulations results tend to be either inadequately cleansing, or high foaming, and thus not suitable for use for cleaning medical instruments, or tend to be unstable and possess an inadequate shelf life, due to denaturing of the enzymes by surfactants employed.
Cheetham (Australian Infection Control, Sep. 2005, 10, 3, p 103-109) compared 17 market leading enzyme based medical instrument cleaners from eight manufacturers (Table 1).
TABLE 1Products compared by CheethamPRODUCTSUPPLIER/MFRCidezyme/EnxolJohnson & JohnsonEndozymeRuhofEndozyme AW plusRuhof3E-zyme/Omni-ZymeMedisafeLapcholyzimeRuhof3M Rapid Multi-Enzyme Cleaner 705003M3M Rapid Multi-Enzyme Cleaner 705013M3M Rapid Auto Multi-Enzyme Cleaner 705053MMatrixWhiteley Med.MedicleanNeodisherMediclean ForteNeodisherMedizymDr WeigertMedizymeWhiteley Med.Mucadont ZymaktivMerzMucapur ERDr WeigerOrthozimeRuhofPacer ReleaseCampbell Bros.PrepzymeRuhof(Australian Infection Control, September 2005, 10, 3, p 103-109)
The products were tested using SDS-PAGE methodology to compare the molecular weights of a group of standardised blood proteins before and after exposure to the various cleaning products. Cheetham reported that half of the products tested, when used in accordance with the manufacturers' directions, exhibited little or no protein digestion, and only two of the products (Rapid 70500 and Rapid 70501—both from 3M and also known as RMEC 70500 and RMEC 70501 respectively) provided a high degree of protein digestion. Cheetham did not report on foaming properties or stability. The present Applicant has tested the two products which provided a high degree of protein digestion and found that one exhibits high level of foaming while the other contains alkylene oxide block copolymer and leaves undesirable oily residues on the treated surface. Moreover, while both exhibit good stability with easily inhibited enzymes, both show poor stability with difficult to inhibit enzymes.
Further, whilst the problem has been outlined with respect to cleaning medical instruments, the desire for cleaning compositions which are efficacious in removing soil and digesting proteins whilst resisting foaming is not limited to the field of cleaning medical instruments. Such properties, along with stability and a long shelf life, are desirable in many different cleaning applications.
A further area where low foaming cleaning compositions are desirable is in the area of air conditioning and cooling. For instance, fresh food cool rooms have their temperature controlled by a refrigeration unit fitted with fans which is integral with the room. The fans draw environmental air through a refrigerated cooling coil heat exchanger into the room. The process of cooling the air results in a lowering of humidity with the moisture being condensed onto the cold surfaces of the heat exchanger. It is well known that any environmental surface which is continually wet or damp will become covered in biofilm. This biofilm not only reduces heat exchange efficiency, but is a very significant potential source of microbiological contamination into the room and is therefore undesirable.
There currently are only limited number of existing methods of removing biofilm from heat exchange coils. The biofilm may be removed with abrasive brushes or high pressure water. This has proved to be problematic because the spaces between the cooling fins are insufficient to allow efficient brushing and the surface areas so extensive as to make this brushing an extremely tedious process. High pressure water has proven to be undesirable because it damages the cooling fins which are made of thin aluminium sections.
Alternatively, the heat exchange coil may be washed with strong alkali or strong acid. This has proved to be problematic because the alkali or acid, whilst eventually removing the biofilm both causes significant corrosive damage to the aluminium fins and the copper refrigeration tubes to which they are attached. This corrosion severely limits the service life of the heat exchange coil.
Thus, it is desirable to have effective yet non-corrosive cleaning agents that act without producing large quantities of foam.
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.